As a typical representative of third-generation semiconductor materials, wide-band gap semiconductors, including GaN, possess a plurality of outstanding performances capabilities which silicon (Si) materials lack. GaN is an excellent semiconductor material for high-frequency, high-voltage, high-temperature, and high-power applications, with great prospects for application in civil and military fields. Due to advances in GaN technology, especially the gradual maturity and commercialization of large-diameter silicon-based GaN epitaxial technology, the technology of GaN power semiconductors is expected to be a technical solution of high-performance and low success rate. Thus the GaN power devices have drawn the attention of famous international semiconductor manufacturers and research institutes.